Lookout-telescope.



A. Kb'me.

. LOOKOUT TELESCOPE.

APPLICATION HLED MAR. 25, I9l5.

- 2 SHEETS-SHEET I;

- Patented Feb. 8, 1916.

A. Kb'me.

LOOKOUT TELESCOPE.

APPLICATION FILED MAR. 26, I915 Patented Feb. 8; 1916.

2 SHEETS-SHEET 2- scopes, in whic xii-scope 1s r1g1d and its upper part. for the 7 UNITED STATES PATENT OFFICE. 4

'ALBER'I KbNIG OF JENA, GERMANY, ASSIGNOR'TO' THE FIRM or CARL ZEISS, or JENA,

GERMANY.

tooK-ouT-TnLEsoo'PE;

To all whom it may concern: .Be it known that I, ALBERT KtiNIo, a "citizen of the German Empire, residing at Jena, Germany, have invented a new and 5 useful Lookout-Telescope, of which the fol-U lowing isa specification. The invention relates to s0 called look-out telescopes, e. to telescopes of fairlvdarge dimensions havingan approximately ver- "tical axis and a horizontal directionof inspection and look-out for observing the country-side from out of a covered pos tion, and more articularly to 'l0()l{-()llt teleli the.lower part of the tele-,

purpose of a variable look-out height, is attached to a mast of adjustable height, so that it is possible to-take the look-out height not greater than the actual cover requires.

S'peciallythe invention relates to look-out telescopes, inwhich the upper part of the telescope carries an objective and a collective lens and in which the lower part of the telescope contains a lens-system of reversion and an ocular.' As with this arrange-.

me'ntthe single rays of each ray pencil passing from the upper part to the lower part do notrun parallel to each other, up to the present, the telescope had to be adapted 3'0 to the different look-out heights by displacing the reversing system, in order to keep the ocularsubstantially in the same position. This lisplacen-ient of the reversing 'system,',luiwever, caused an undesired con- 35, ,siderable change of the power'of the tele; scope and thereby a, considerable change of;

the size of that part of the country-side, w'vhich is visible in the telescope. Accorcb ing t0. the invention this change of power to may be' considerably reduced by composing the reversing system of two members, a

rigid front member and-a displaceable rear member, the front member being positive and ,having the greater. (absolute)' focal 1 5 length. lVith such an arrangement the "power may be kept constant the better, the smaller the focal length of the displaceable member. In order to keep the power quite" constant or nearly, constant, the focal length 5 0 of the-rearmember of the reversing system -Would have to be so small, that the practical performance was attended with difficulties. The same result, however, is obtained without. getting practically too small "focal Specification of Letters Patent.

lengths, if, beside the rear member, the front membertoo be disposed displaceably.

-In the annexed drawing l i'gures 1 and 2 duigrammatlcally show some optical systems, the progress caused by the invention to be illustrated by means of these figures by some numerical examples; Fig. 3 showsin a' longitudinal section a constructional exam of the reversin svstem Fig. 2 the )osition of the two members of the reversing system) corresponding to two different look-out heights. In both figures the objective image plane forming simultaneously the front image plane-of the reversing system is in dicated, in each ofits two different positions by a dotted line .while the ocular focal plane, which coincides with the rear image plane of the reversing system'and is 'to' keep its position unaltered, is shown by a dotted line 0 -0 I In Fig. l a reversing system "a ofthe focal length F=1 is assumed. In the drawn dispositionl the distance between the objective image plane and the reversing system is P 11 and the distance between the reversing system and the ocular focal iilane Z 11, therefrom the power corresponding to the image formed by the reversing system" results' as L =0.1.[ In th' disposition II the.

upper part of the telescope is assumed to be let down so far, that the primary distance between the objective image plane and the ocular focalplane has decreased from 12.1

to 4. ,In order that the rear image plane of the reversing system keeps its position, the

reversing system is to be displaced toward the objective for an amount of 0. 9, so that Z :Z ':2. Consequently the power corresponding to the image formed is N=1=1and thus, compared with that corresponding to the image formedin the disposition I, increases to the tenfold amount;

In Fig. 2 the reversing system is assumed to be composed of tWo positive members, the front member a having 1a focal length F =1 and the rear member having a focal length I 0.25. The look-out height corresponding tothe disposition I;of therdraw- Patented Feb. 8, 1916, I Application fileii March 26, 19 15. Serial No. 17,300.

ing is taken the same as that corresponding to the disposition I of Fig. 1. The distance between the objective image plane and the front member 14 is 1 :11, thedistance between the two members u and 11. Z:1.1. The rear member a is fitted in the ocular focal plane O O. As in this position the ,member a does not influence the imaging the power corresponding to such an arrangement is again N 01 as in-the disposition I of Fig. 1. In the dispositions II and III the look-out height is assumed to be the same reduced one as that in the disposition II of Fig. 1, so that the distance between the objective image plane and the ocular focal-plane also amounts to 4. In order to adapt the telescope to the smaller look-out height, in the disposition II only the rear member a? is displaced, while the front member u keeps its place. Henceit follows Z :2.9, and the other distances result according to the condition that the rear image plane is again supposed to keep its place as 1:0.923 and Z :0.177. The power corresponding to such an arrangement results as 1 =0.154 and thus compared with that corresponding to .the 'disposition I, has increased only to the 1.54- fold amount. In thedisposition III both members of the reversing system are moved out of their place hold in the disposition I, and in order to form again an image in the ocular focal'plane the following distances are-chosen: Z :3.227 1:0.579; 1 -0194. The power obtained with such an arrangement results as.N':0.1 and thus equals the" power obtainedwith the disposition I.

In the constructional example of a lookout telescope according to the invention, shown in Fig. 3 of the drawing, the rear member of the reversing system of this telescope being disposed displaceably. I11

structure.

this example .the upper part of the telescope being adjustable in the height-direction and containing as optical parts a reflecting prism a, an objective I) and a collective c,

which is disposed in the image plane of the objective, is carried by a telescopic tubular system (Z, which is mounted laterally of the optical axis on a frame d forming the suba greater The moving of the tubular system is efi'ected by means of a compressed gas, which is obtained from a steel bottle 03 and is conducted to the interior of the tubular system by. a three-way cock'd The frame (1 serves as carrier'ofthe lower part of the' telescope, which contains 'as optical parts a reversing system comprising two members e and e a reflecting'prism f and an ocular system-9 ,9 The front member 6 of the reversing system is "fitted immovably in the casing, while the rear member e is fixed .to a bushing k, which by means of two extension pieces 71, and k is guided in the direction of the axis of the telescope You two spindles it I and 75*, which are mounted'within the vcasing. Of these two spindles one, h, is threaded as well as the corresponding extension piece 72 of the bushing h and can be turned by means of a I pair of bevel wheels k h and by a hand wheel 11. which is disposed outside the casing, so that, for adapting the telescope to the look-out height chosen, the member a of the reversing system can be displaced in lens-system of'revision and an ocular, which lens-system of revision consists of two members,-a front member'and a rear member, the front member'being positive and having (absolute) focal length than the rear member, of which two members at least the rear member being disposed .displaceably in the direction of the optical axis.

ALBERT KoNIG.

I Witnesses:

PAUL Kniionn, RICHARD. HAHN. 

